1. Field of the Invention
The present invention is directed to ink compositions and, more particularly, to aqueous ink compositions suitable for imaging applications, such as ink jet printing processes.
2. Discussion of the Related Art
Ink jet printing is a non-impact process wherein droplets of ink are produced and deposited on a substrate such as paper, transparent film, or textile material in response to an electronic signal. Ink jet printing systems are typically classified by two known types: continuous stream or drop-on-demand.
Ink compositions which are useful in imaging applications, such as ink jet ink printing systems, are well known and generally contain water soluble dyes. Also known is the addition of suitable cosolvents systems such as glycols and other humectants to such dye based ink compositions in order to improve the latency and recoverability in printers utilizing such compositions. See, for example, U.S. Pat. No. 5,389,133 to Gundlach et al., U.S. Pat. No. 5,286,289 to Winnik et al., U.S. Pat. No. 5,271,764 to Winnik et al., U.S. Pat. No. 4,840,674 to Schwartz, the specifications of which are incorporated herein in its entirety by reference.
Although dye-based inks are suitable for their intended purposes, dyes have several disadvantages when used in ink jet inks. For example, dyes, being water-soluble in a water/organic mixture, may dissolve and run when exposed to moisture or water. Dye images may further smear or rub off on contact with felt pen markers or upon being rubbed or touched by finger. Dyes also exhibit poor light stability when expose to visible or ultraviolet light.
Pigments are also known as colorants in ink compositions but have not received a wide degree of acceptance in ink jet ink systems, for example, because of problems associated with the performance and reliability of the composition, i.e., print properties, stability, latency, and the like.
As a result, although known compositions are suitable for their intended purpose, a need remains for improved ink compositions, especially for use in the ink jet printers, which overcome the problems typically associated with current dye-based and pigment system. In addition, there is a need for improved ink compositions which exhibit improved latency and recoverability in their respective printing systems while providing good print properties.